Conventionally, a fuel vapor treatment apparatus, in which fuel vapor generated in a fuel tank of an internal combustion engine is recovered by a canister, is known. The fuel vapor recovered by the canister is supplied to an intake passage and is used for burning in the internal combustion engine. In Patent Document 1 (JP 2004-11561A corresponding to US 2003/0226549 A1), an open/close valve is provided in a passage which connects the fuel tank and the canister, so that isolation between the fuel tank and the canister is ensured in a fuel vapor leak check. Thus, accuracy of the fuel vapor leak check is improved. In Patent Document 2 (JP 2006-69359A), a fuel solidifying agent is mixed with fuel in a fuel tank, thereby preventing breakage of the fuel tank when a collision of a vehicle occurs.
However, in the fuel vapor treatment apparatus described in Patent Document 1, if the open/close valve is closed when the collision of the vehicle occurs, the fuel tank may be broken by an internal pressure in the fuel tank. In a fuel vapor treatment apparatus described in Patent Document 2, if the mixing of the fuel solidifying agent with the fuel is insufficient, the fuel tank may be broken when the collision of the vehicle occurs.